Electron discharge device



March 27,1945. H. K. ISHLER 2,372,379

7 ELECTRON DISCHARGE DEVICE Filgd May 19, 1943 "W i w: l a T574.

INVENTOR fikmwy KIN/v57 [SHLf/P ii N? The development of hearingPatented Mar. 27, 1945 UNITED STATES PATENT {QFFICE 1,372,379 if:ELECTRON mscnaac'nnnvron I Harry Kenneth Ishler, Emporium, Pa., assignorto Sylvania Electric Products Inc., Emporium, Pa., a. corporation ofMassachusetts Application May 19, 1943; se ial No. 487,561 2 Claims.(Cl. 250217.5) I I This invention relates to electron discharge devicesand in particular to the design of electron tube units of light weightand small dimensions.

Most of the various sizes and shapes of radio receivin tube types usualon the market about ten years ago have now been replaced by a singleshape and size, considerably smaller than the average size formerlybelieved necessary for good performance. This form to which the olderreceiving tube types have converged is substantially that of a standardcalled lock-in tube. No serious demand for a smaller radio receivingtube seems to exist at the present time, and a proposed furtherreduction of size apparently did not correspond to any existing demand.

An actual need for a considerably smaller electron discharge tubeexisted, however, in applications other than radio broadcast reception.Representative of this demand are hearing aid sets, in which a reductionof the weight and size of amplifier tubes to the absolute minimumobtainable for the present status of the art is of immediate practicalimportance.

aid tubes has therefore led to a further improvement of the artconnected with a considerable reduction of tube size, so that it is nowpossible to manufacture these exceedingly small tubes with practicallyno sensitivity against mechanical shock or handling. Accordingly, aprincipal object of the, invention relates to the reduction of theweight of theelectrodes used in extremely small electron dischargetubes. I y 1 ;A feature of the invention relates to a small.sizeelectron discharge tube in which the. heat radiation from the anodeis increased, compared to the heat radiation obtained from a largersizeanode in a tube of similar dimensions.

Another object is to 'providea plate construction whichcan be formed bysimple punching and shaping operations on a singlesheet of metal.

According to another object of the invention,

means are provided to reduce the output capacity of a small filamentaryelectron discharge tube with a single strand filamentary cathode.Another principal object is to provide a plate construction for electrontubeswhich facilitates examination of the electrode assembly during orafter manufacture, and the ancillary object of expediting the outgassingof the metal parts.

According to still another object of the invention, the ratio of theinterelectrode capacity. between filament and control grid to thatbetween filament and anode can be adjusted to any desired value withinlimits.

A feature of the invention relates an extremely small electron dischargetube having a minimum variation of input capacity over'a wide frequencyband.

Another feature of the invention relates to a ru e o new method whichpermits the reduction of certaininterelectrode capacities of an electrondischargetube without increasing the size ofthe bulb or providingseparate lead-in seals through different parts of the envolepe.

still further ieatureof the invention relates tures, each single. one of which is, in the usual tube constructions obtained at the expense ofsome of the others. For example, the reductionof interelectrodecapacitances may be achieved by the introduction of additional shieldingelectrodes (e. g., screen grids), which however, increase the weight andeventually the size of the tube. Or it by increasing the size of the en'maybe obtained velope and carrying the lead-in conductors through widelyremote parts of the envelope.

-This not only changes the tube size but it also leadstoundesirablesealing-in processes and may not be consonant withexistingcircuit requirements. a

H filsually a reduction of the mass of the electrodes results in adecrease of the mechanical the tube, and a reduction of its ability .toradiate large quantities of heat at low temperature. According to theinvention, means are provided whereby the mass of an electrodeisdecreasedwhile its heat dissipation ability during-actual-use,issimultaneously increased. Or-

..dinarily, an increase of heat radiation surface of an electroderesults in an increased size and weight of this electrode.

According to the invention, all these difficulties areavoided by anovelmethod of mounting and a change of shape of some of the electrodes,which permits a simultaneous achievement of these various ends withoutany sacrifice of space or simplicity of {the various other stepsnecessary for manufacturing a finished tube.

Theinvention will nowbe described in connection 'with the drawing, inwhich, A Fig. 1 is a cross-sectional view of a triode mount withfilamentary cathode, built for high mechanical sturdiness, and providedwith large radiating vsurfaceof the anode, correspondingto prior dei n-V I v Fig. 2 is a side view of the same triode mount. 1 Fig. 3 shows across-section through a similar triode,-but improved according to theinvention.

Fig. 4 gives a side view of the mount of Fig. 3.

Fig. 5 is an elevational view of the plate shown in Figs. 3 and 4.

The triodemount illustrated in Figs. 1 and? consists of a headerorstem'l through which are sealed lead-in connections 2, 3, 4, 5, etc.The plate 6 is supported by four plate support wires 1, 8, 9, l0,attached in any well-known manner to the mount spacers II and 12,preferably made of mica sheets. Also attached to these upper and lowermount spacers are grid supports; [3 and M, on which is wound the gridwire l5, also in a manner well-known in the art. Filament I6 is threadedthrough central holes the iin'oun't spacers, and the lower end offilament i6 is connected to one of the lead-in wires 3. The upper end ofthe filament held taut by him? corrvenient filament tension spring l1,the end of which is welded to filament tension spring sup-'- port [8, bymeans of a fi lainent tab 1 9.

The filament voltage may be applied to the filament l e at the rue-meatlead a and the filamen't spring support lead 2-0 as shown in the figure.It is of e'eur'se understood thatgfid and plate of the tube arei'sonhe-ted 't'o s'dl'he Cohveniently located lead in eendire'te'rsKnetshewn in the figure) in the header l.

Filament and grid ere completew susreunded by a box-like anodestructure, whereby the grid structure is -electrostatically shielded bythe anode from the filament tension spring "support. The -plate-t gri dcapacity comparatively large,-due to the ra'ct that the grid is'eemme'tely surrounded by the anode. This construction is very sturdybecause oi the four plate supports and the sidewalls 2] 22, and "endWalls 2; 24, of the-plate hex, Which 'proV-l'd'es -grea't Stifiness tothe plate structure. The' plate walls are solid surfaces and theoontihua-tions "2 5, -'26, 21

and 28 of the active plate walls {21 and 22, iii- *crea'se the radiationsurface of the plate, so as to permit a. "greater heat dissipation. g

in Figs. 3-5 is 'sh'ow'n the new iis ih according to the invention, inwhich the plate sh'aiJ ahd the position (if the fila-mnt te'h's'iohsuppert are so modified as to result in a lowered plate *to id capacity,and an increased inherent capacity between the filament tension spring18, and the grid I 5,while the -charactieristics*of the electrondischarge space are not ch'an'ged com- "pared with the design or Fig.*1. It should noted that the large ih herhtoapabity resulting from thee1o'se ess of fileim'eht tension ratio of the effective interelectrodecapacities between filament and grid on the one hand to that betweenfilament and plate on the other hand, merely by shifting the position offilament support I8 along the dotted line arrows (Fig. 3).

The cooling of the plate is made more effective by bending the platewings 29 and 30 outward and away from the discharge space much closer tothe area of maximum electron dissipati'o'n near the gr-id laterals, asindicated by the full-line arrows which suggest the discharge path.

support 18 (in Fig; 1 to '-the=end'wall' 23 '61 the I plate iscompletely eliminatedfin the construetion shown in Figs. *3 and'-'rhe'distance between l8 and the plate wings29and 30in 3,

"reduces the output capacity very appreciably.

Inspection "er Figs. 1 the s also enews directly the way in which,according to the invention,

the low grid to 'filament -capacity=of Fig. this: i

stan'tially due to the shielding effect bfthe plate when located betweenfllafiner'it ttiiisioitt spring support I8 and grid 4 5) is inora'seti'in Fig. 3*by removing the 'shieldiii'g e'iid tv'a'll 28 hf the plate,and thus permitting some "o'f the electric lines of force from thesuppcrt l8 t'o eiiddirectly on the grid 45, without interception.

Furthermore, reinoval "of this plate 'en'clytfa ll.

in Figs. 3-5, decreases the plate-*to 'grid "CQPMTW,

as compared with the closed box constructioii of Fig. 1.

Finally, it is obvious that in the construction er Figs. --3-5, it 'isalways possible to 'adjus't the As may be seen more clearly from Figs. 4and 5, the weight of the plate is appreciably reduced by openings in thewings and rib of the anode, which are not eleotiioally active in this"design.

1 It should be noted that the plate electrode in Figs. 3 and "4, issupported by only three plate supports 3|, 3'2 and 3'3, a "compared tothe four plate supports needed in the prior design o'f'Fi'gs. l and '2.one might expect at first sight that the support has been weakened bythe omission of one r 'theip'reviously used jplat'e supports. This is,however, not thecase, as will be easily understood from "the followingconsideration. The total weight of the anode of -Figs. 3- 5 is smallerthalh'that of the closed box-anode oi Figs. 1 and '2 for two reasons.'The run length of the metal strip needed ffor forming the anode isshorter than that needed for forming the boxplate at Fig. 1.Furthermore, some of themetal stock of the new plate is eliminated bypunching o'ut holes from the ribs and wings, as mentioned before inconnection, withFigs. 4 and '5.

In one typeof tube oi this kind .actually being built, the total weightof ,theanode has beenreduced to about 60% ofi-ts original weight whilepreserving the other desirable characteristics of the .prior plate. IAccordingly, the load per plate support in the new construction isreducedto only of the weight which each one of the our plate supports:had to carry in the older design, even though the number of :platesupports has been reduced. It will be clear that the invention is notlimited in spirit or scope to the iparticularembodiment disclosed, andthat various changes and modifications can be .made therein as will heapparent afterconsiderihg the foregoing description and the appended.claims.

WhatI claim is: I

-1. An electrode fo'r electron d-lscharge tube's, comprising ametalstrip beht to tennis. troughlik'eshape in "transverse section, the edgesof the trough being bent back and iormin'g' diverging wings the maintrough-like portion being Zunperforated to act as an electron receivingelectrod'ean'd said bent back'wings be'in'g perforated, and tesuppor tthe electrode adjacent the edges of said wings arid-adjacent the b'a'seof salid trough, *sa'id supporting 'r'ri'eans being positioned--in'-triangular -array, I I

2. -'A ftub'e mount comprising a header carryin'g a plurality o'f-"electrode-suppcrtrods, -'a pla'tehlectrode supported-on three of sa'i'drods arranged an triangular array, said plate being of meta'lb'ent backupon itself to-form a *constric'ted -'chan'nl to receive one -o'f sailrods *and an enlarged "trough-like section serving as {an electronohahrber, the edges of said trough-likes'ectioh bein'g gbent backandoutWa'rdIy 'diverg'ing and'attached to respective support rods. I"ISHLE' R.

